<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>v-if</title>
</head>

<body>
    <div id="app">
        <input type="button" value="测试使用" @click="toggleIsShow">
        <p v-if="isShow">测试</p>
        <h1 v-if="tem>=40">太热了</h1>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        var app = new Vue({
            el: "#app",
            data: {
                isShow: false,
                tem:45
            },
            methods: {
                toggleIsShow: function () {
                    this.isShow = !this.isShow;
                }
            }

        })
    </script>

</body>

</html>